1. FIELD OF THE INVENTION
The present invention relates to a method and apparatus for removing oxidizable contaminants in cooling water used in conjunction with a cooling tower. A general principal of science is that on passing from a liquid to a vaporous state, every liquid absorbs heat and subsequently gives off this heat again on condensing back into a liquid from the vapor state. In cooling apparatus employing this principal, a liquid is converted to a vapor state to absorb the heat and provide the required cooling. The vapor is then passed to a condenser where the vapor is re-converted into the liquid in order to go through a subsequent cooling operation. When the vapor is converted back into a liquid in the condenser, heat is generated. In order for the condenser to operate efficiently, this heat must be removed from the condenser coils. Cooling waters are used to run over condenser coils in a cooling tower, to thereby create a heat exchange process and transfer heat from the condenser coils to the water. The cooling water is exposed to air where the heat absorbed by the cooling water is dissipated into the atmosphere. The recirculating cooling water is usually drawn from a standard source such as public water, which may contain microorganisms and other contaminants. Through running over the condenser coils and exposure to the atmosphere during the heat dissipation process, the recirculating water becomes further impregnated with microorganisms and other contaminants. The microorganisms and contaminants in the water serve to corrode the condenser coils while the cooling water runs over them. This corrosion impairs the heat exchange process and further creates costly downtime during which the condenser coils must be cleaned or replaced. Some of the impurities can be removed through conventional filters. However, many organic impurities and other inorganic solids are not removed by conventional filtering means. The present invention provides a system whereby the impurities are significantly reduced and/or removed from the recirculating water to thereby substantially reduce the corrosive effect on the condenser coils.
2. DESCRIPTION OF THE PRIOR ART
One key element of the present invention purification process involves the concept of reducing the oxygen demand in the recirculating water stream. Since the contaminants which are not removed by conventional filtering systems are usually oxidizable materials, the oxidation of such materials serves to degrade and eliminate them. This concept is described in general terms in the paper "Innovative Oxidation Technology for Waste Pretreatment", by Stanley A. Peterson and Nicholas S. Zaleiko, which was published in the February 1981 issue of Water/Engineering and Management ("Oxidation Article"). The method described in the Oxidation Article is an improvement over a previously known "wet oxidation process" which is used to treat municipal and industrial aqueous effluents containing oxidizable organic compounds. The wet oxidation process comprises forcing compressed air through the heated effluents (heated to temperatures of 150 degrees centigrade to 320 degrees centigrade) under pressure (300 to 3000 psig) in the presence of cupric ion as an oxidation catalyst. Under conditions of the process, organic compounds present in the effluent are degraded by sequential oxidation to carbon dioxide, water and refractory organic compounds such as formic and acetic acids. Additional treatments are required to remove the refractory organic compounds. As discussed in the Oxidation Article, the process described therein includes subjecting the liquid to be purified to cavitation, adding a free radical initiator, including supplementary cavitation and exposing the liquid to ultraviolet (UV) light. When cavitation is applied, the bubble explosion in cavitation ruptures the thin cell membrane of microorganisms. In addition to oxidation by the free radical, the exposure to ultraviolet light provided for additional free radical oxidation.
The process discussed in the oxidation Article was further described in a patent application filed by Nicholas Zaleiko entitled Method and Apparatus For Oxidative Degradation of Water Contaminants. That application was subsequently abandoned.
The above referenced application and the Oxidation Article concentrated on removing impurities from waste waters and specifically concerned the following:
(1) Oxidation of process chemicals such as dyes, fatty acids, sludges and certain organics;
(2) Sanitary and industrial wastewater treatment at remote locations;
(3) Specific industrial wastes such as cyanides, sulfites, phenols, fat renderings, food processing pigments, pharmaceutical, soft drink and alcohol-type wastes;
(4) Pulp and paper bleaching and processing;
(5) Semicatalytic oxidation of refractory compound such as those from plating and photographic wastes;
(6) Treatment of various in-plant side streams such as digester supernatant and thickener overflows;
(7) Destruction and treatment of septic wastes.
This prior art process concentrated on the above applications and did not expand the treatment process to other applications such as Cooling Towers. In addition, inventor Zaleiko included several complicated steps such as heating the liquid. The present invention greatly simplifies the process and utilizes it in a new and non-obvious application.
The inventor is also aware of the following prior art patents which relate to various purification and treatment processes:
1. U.S. Pat. No. 2,722,498 issued to Morrell et al. in 1955 for "Process For Separating Organic Material From Inorganic Material".
2. U.S. Pat. No. 3,288,295 issued to Kelly in 1966 for "Tank Cover Structures".
3. U.S. Pat. No. 3,401,115 issued to Meyer et al. in 1968 for "Sewage Treatment System".
4. U.S. Pat. No. 3,480,543 issued to Hildebrand in 1969 for "Process And Apparatus For Disinfection Of Sewage".
5. U.S. Pat. No. 3,672,823 issued to Boucher in 1972 for "Method Of Sterilizing Liquids".
6. U.S. Pat. No. 3,677,409 issued to Ferm et al. in 1972 for "Sewage Treatment System".
7. U.S. Pat. No. 4,013,552 issued to Kreuter in 1977 for "Sewage Treatment Process".
8. U.S. Pat. No. 4,076,617 issued to Bybel et al. in 1978 for "Sonic Cavitation And Ozonation Of Waste Material".
9. U.S. Pat. No. 4,144,152 issued to Kitchens in 1979 for "Dehalogenation Of Halogenated Compounds".
The processes described in the above patents differ from the Oxidation Article and the abandoned Zaleiko patent application, and also differ from the specific application to Cooling Towers of the present invention.
The inventor is also aware of the following patents which disclose various apparatus and/or methods by which cavitation and other shock treatments are employed in a cleaning process:
1. U.S. Pat. No. 2,660,564 issued to David in 1953 for "Method Of Reducing The Density Of Aerogels And Similar Materials".
2. U.S. Pat. No. 2,832,545 issued to Segraves for "Supersonic Jet Grinding Means And Method".
3. U.S. Pat. No. 2,911,787 issued to Barry in 1959 for "Inlet Probe".
4. U.S. Pat. No. 3,265,090 issued to Elliott in 1966 for "Fluid Flow Controller".
5. U.S. Pat. No. 3,278,165 issued to Gaffney in 1966 for "Method And Apparatus For Generating Acoustic Vibrations In Flowing Fluids".
6. U.S. Pat. No. 3,504,945 issued to Leibundgut et al. in 1970 for "Pneumatic Conveyor System".
7. U.S. Pat. No. 3,538,803 issued to Joseph in 1970 for "Cavitation Machining Apparatus".
8. U.S. Pat. No. 3,674,216 issued to Blair in 1972 for "Treating Liquid Waste Effluent".
9. U.S. Pat. No. 4,053,110 issued to Schalkowsky et al. in 1977 for "Shock Press".
10. U.S. Pat. No. 4,284,245 issued to Fishgal in 1981 for "Machine Lubrication System".
11. U.S. Pat. No. 4,506,834 issued to Ek in 1985 for "Method And Device For Dispersing Material".
While there are many prior art references dealing with the inducement of cavitation and other shock effects utilized in purification processes, none of the references disclose the concept of the present invention treatment process used in conjunction with cooling towers.
Much work has been done on microbial control and treatment systems employing chemicals to destroy the micro-organism present in recirculating water. These systems, commonly used in large water re-circulation systems are chemical treatment processes involving oxidation of the organic material, have a high cost and maintenance as well as presenting some hazard to the operators.
A need has developed for a compact and reliable treatment system employing free-radical chemical reaction capabilities of auto-oxidation of both organic and inorganic materials present in water enhanced by the addition of catalysts so that the reactions can be induced to rapid completion by high energy transfer. Prior art of aerobic or chemical treatment systems have not satisfied the need.
There exists a significant need to clean the recirculating water system of cooling towers by an efficient and cost effective process to thereby (i) enhance the cooling tower operation by eliminating the rusting of the condenser coils which rusting degrades the heat transfer process and (ii) further reduce down time maintenance to clean or replace rusted condenser coils.